Unfamiliar w/ Particular Requirement by Building Department

[andrew.tkelly]

Hi,

I am designing a commercial, rooftop PV system, and we will have to do a line-side tap on a commercial switchboard.

The building department wrote me that the switchboard w/ the tap installed has to be re-certified by a 3rd-party and designed by an electrical engineer.

I understand the second part --that as they want an electrical PE to stamp the plans, but what do they mean about re-certification of the switchboard w/ the tap installed? How do I even start that process? Who would I go to? Sounds expensive!

Thanks in advance!

Kind Regards,
Andy

 

[ron]

Because you are modifying something that is UL listed and tested in a particular configuration

https://services.ul.com/service/field-inspection-service/

 

[electrofelon]

Not sure how much you know about the specifics, If you have had your eyes on it, but I wonder if there is an option of changing out the lugs for ones approved by the manufacturer that would meet your needs. Maybe they will go easier on you if its all "approved" stuff. If the switchboard has metering provisions, then yeah thats not going to work as you would be forced to hit the bussbars. I have had to do such a thing a few times, but have always gotten lucky and the AHJ says just use listed lugs and dont drill holes and you're fine.

 

[raider1]

HERE is a link to a white paper written by UL that addresses tapping of buses in Switchboards and Panelboards.

Panelboards and deadfront switchboards are not Listed to have their busbars tapped unless there are existing holes in the busbars marked with the word “Tap” adjacent to the holes. Other holes in the busbar that are not marked with the word “Tap” are intended for the connection of overcurrent devices, other device’s as identified by the product markings and in the installation instructions or other uses identified by the manufacturer.

When the electrical equipment Listing does not include product markings or instructions for tapping busbars this should be treated like any other modification of a Listed Product. That would require a field evaluation of the busbar tap.

You would want to contact a Certified Field Evaluation Body to perform a Field Evaluation.

UL can provide field evaluations, if you are interested in more information regarding UL's field evaluations please PM me.

Chris

 

[ggunn]

Hi,

I am designing a commercial, rooftop PV system, and we will have to do a line-side tap on a commercial switchboard.

The building department wrote me that the switchboard w/ the tap installed has to be re-certified by a 3rd-party and designed by an electrical engineer.

I understand the second part --that as they want an electrical PE to stamp the plans, but what do they mean about re-certification of the switchboard w/ the tap installed? How do I even start that process? Who would I go to? Sounds expensive!

Thanks in advance!

Kind Regards,
Andy

Will the AHJ allow you to connect to the service conductors on the line side of the switchboard OCPD inside the enclosure via insulation piercing connectors? Most that we deal with will allow it.

 

[electrofelon]

Will the AHJ allow you to connect to the service conductors on the line side of the switchboard OCPD inside the enclosure via insulation piercing connectors? Most that we deal with will allow it.

Yeah that's what I was thinking, lugs or tap onto conductors. I don't see how they can require recertification or even engineer approval for that. Isn't that what we have electricians for?

 

[ggunn]

Yeah that's what I was thinking, lugs or tap onto conductors. I don't see how they can require recertification or even engineer approval for that. Isn't that what we have electricians for?

Most commercial PV systems here in Texas are required by AHJ's to carry a PE stamp on the plans. It's not related to the method of interconnection.

 

[andrew.tkelly]

Thanks for the all the info, guys. I just got off the phone with UL's program manager of field evaluations. They said they can send a field inspector to certify it for somewhere between $3-5k. That's not as bad as I thought it would be.

As far as using insulation piercing conductors to connect to the line side of the service entrance conductors, I will ask the AHJ.

 

[andrew.tkelly]

Also, just for own learning, it seems there are four ways to connect in a switchboard:

1. Have the inverter output circuit protected by OCPD in the switchboard
2. Do a line-side tap on the switchboard's busbar (usually has to be inspected by a NRTL field inspector)
3. Use insulation piercing conductors on the service entrance conductors on the line-side of the switchboard OCPD
4. ...and something about lugs? Can someone explain in detail about replacing the lugs to connect PV?

If there are any other ways of interconnecting on a commercial switchboard, please let me know just for the sake of knowledge. Thank you!

Andy

 

[texie]

Thanks for the all the info, guys. I just got off the phone with UL's program manager of field evaluations. They said they can send a field inspector to certify it for somewhere between $3-5k. That's not as bad as I thought it would be.

As far as using insulation piercing conductors to connect to the line side of the service entrance conductors, I will ask the AHJ.

Your post sort of implies a large service which likely means parallel conductors. If you have parallel service conductors tapping them can become very complicated and expensive as all the conductors of each phase would have to be tapped as one.

 

[electrofelon]

What I meant by the lugs option , is to replace the main switchboard lugs with ones with more ports (if possible).

Another option would be to connect to the feeder bus. I know that is very similar to your #2 with probably the same implications, but you did specifically refer to the line side.

 

[electrofelon]

And just for completeness, some modifications to your #3. There are many other ways to pull another set of service entrance conductors off your existing SECs besides IPCs (personally, they would not be my go to method, but everybody has their preferences). A "polaris" type connector where the conductors can pass thru the block would be a good option. Something like this may work:

https://hubbellcdn.com/ohwassets/HCE/cmc/catalogues/pedestal-connectors.pdf

There is all kinds of stuff out there

 

[pv_n00b]

Also, just for own learning, it seems there are four ways to connect in a switchboard:

1. Have the inverter output circuit protected by OCPD in the switchboard
2. Do a line-side tap on the switchboard's busbar (usually has to be inspected by a NRTL field inspector)
3. Use insulation piercing conductors on the service entrance conductors on the line-side of the switchboard OCPD
4. ...and something about lugs? Can someone explain in detail about replacing the lugs to connect PV?

If there are any other ways of interconnecting on a commercial switchboard, please let me know just for the sake of knowledge. Thank you!

Andy

Busbar clamps. See page B-52 of this catalog for an example. The catalog is a pretty large download.

 

[electrofelon]

Busbar clamps. See page B-52 of this catalog for an example. The catalog is a pretty large download.

Neat, good info. Never heard of those.

 

[jaggedben]

Busbar clamps. See page B-52 of this catalog for an example. The catalog is a pretty large download.

Interesting. So does using something like this typically still require field listing?

 

[pv_n00b]

Interesting. So does using something like this typically still require field listing?

I heard of these recently from a PV contractor who has been using them and AHJs have not been requiring field recert but I have not used them on any projects I have been involved with. In the end it's going to be up to the AHJ, but since these don't require drilling, removing existing bolts, or other changes they seem to not elicit the same level of scrutiny. I'm hopeful. I would have used these on a project that was just interconnected but the contractor could not track down a source for them in the time we had.

Another clamp is the Burndy YG14BTC28 which is cleaner than the other but requires compressing the clamp onto the busbar with a tool. Might be a more difficult access wise. But options are good.